Vintage Mustang Forums banner

My 68’ Factory A/C Thread

504 Views 12 Replies 4 Participants Last post by  matnetik
I have 68’ Mustang with factory A/C. I have been wanting to fix the A/C for some time now and was planning on doing it during the winter. Well the other day I had to drive the car at 7am and the windows were all fogged, defroster didn’t do a thing, luckily once it got in the sun it cleared up. Just to be clear, I have the shop manual and vac/wiring diagram.

Here’s what I know -
-brand new compressor, charged and blows cold
-only blows on the feet
-firewall heater hoses are disconnected
-took a quick look behind the control panel, looks like there isn’t anything attached to control where the air flow goes
-when the compressor is connected and the a/c switch is on, it runs all the time and never shuts off


Here are some of the parts I have but are not installed-
-a/c thermostat
-new vacuum line kit (color-coded)
-water heater valve & hoses

I currently have the vacuum line disconnected from the carb but it normally runs from the carb to a vacuum reservoir (brand new) in the fender-well, then out of there to a vac port in the firewall, the other port from the firewall is what connects to the water valve if I am not mistaken.

Going to take this one step at a time, take things apart, put the new parts in and get it all connected. Am going to take pictures along the way to help others. Any advice is welcomed, needed, and much appreciated on where to start and what to look for!

First question, before I connect the firewall heater hoses, is there anything I need to look at for or do? My car currently looks like the picture this:
Hood Motor vehicle Car Automotive design Automotive exterior

hose goes straight from the manifold to the water pump, I need to get the water heater valve and hoses to the firewall connected.
1 - 13 of 13 Posts

· Registered
Joined
·
662 Posts
You have a nice looking engine compartment. I’d buy this Molded hose for the water valve to heater core:


You can use regular hose but it won’t be as neat. The other two heater hoses you can buy concours but I like regular gates heater hose just fine for them. I can only seem to find it at OReiileys.


On the vacuum lines if your dash controls are original they have little colored dots beside them. Try to do one line at a time. Follow the diagram.

a mityvac hand pump can be useful for diagnosing just don’t overdo it as you can rupture old vacuum Servos if you pump it too much
 

· Registered
Joined
·
662 Posts
I forgot to add that the original heater hoses do have a 90 degree bend at the end. You can get them at NPD as well reproduced. I don’t think they are as needed as that one I listed above.

there is also this Dayco Hose with a 90 already molded in:

Font Rectangle Parallel Screenshot Circle
 

· Registered
Joined
·
1,187 Posts
As an aside, your good looking engine compartment could be even tidier if you rotated your a/c comp. 90* clockwise. It would put your hoses on the side and under your mc bar. kip
 
  • Like
Reactions: matnetik

· Registered
Joined
·
8,201 Posts
As an aside, your good looking engine compartment could be even tidier if you rotated your a/c comp. 90* clockwise. It would put your hoses on the side and under your mc bar. kip
Depending on the model of compressor they may have to be on top.
 

· Registered
Joined
·
8,201 Posts
I added factory AC to my 68. I had to search for all the original parts and restore them so I ended up doing extensive research on these systems, so I have lots of pics and documentation on them. I also spent a lot of time talking with Classic Auto Air about them.

From your pic, I can see the vacuum line going into the vac canister, but I can’t see it leaving. Might just be the pic. The hose should come from the back of the manifold on the vacuum tree to the vacuum canister. From the canister it goes through the firewall. If you have any vacuum accessories you might have a splitter with a check valve in it.
Check Valve - Headlight / Tilt Away Column Vacuum System - Repro ~ 1967 - 1970 Mercury Cougar / 1967 - 1973 Ford

The 68 canisters should have a check valve in it, but the repros I have used suck, so you might want to add an external check valve. Once through the firewall the line goes to a tee. One (Purple) line goes to the water valve vacuum switch, then back out the firewall to the water valve. The other line (Black) goes to the vacuum regulator (control switch). From the regulator you have red, white, and blue lines out to control the defrost, outside/recirculating, and A/C vs Heat door motors. There is also another tee in the red line and as it goes to 2 motors, 2nd hose is green.

The heater hoses are not needed for the AC system to work, but obviously you want them for the heater. The water valve needs to be checked for a vacuum leak though.

From your description, you have a vacuum problem. It could be the hoses, the tees, the check valve, motors, or the regulator. You need to track down the leak or leaks. I had at least one regulator, the simply didn’t work and wouldn’t send the vacuum to the right places. the tees are prone to breaking too. There is a nice little pamphlet on the system that will help you.

Wheel Tire Car Vehicle Hood


It has a diagnostic chart and lots of good illustrations.

The system does not have a low pressure cut off switch so you have to be careful not to run it when pressure is too low. (Or add a switch).

i would start by working from the manifold out, checking for vacuum at each point in the hoses to see when there is a leak.
 
  • Like
Reactions: matnetik

· Registered
Joined
·
1,187 Posts
Sanden style compressors can be rotated 90* either way, the only thing you can't do is put the oil plug on the bottom. Sanden scroll compressors cannot be rotated, his is not a scroll type. When I bought my 65, the po had installed mine like matnetiks, so I changed it. kip
 
  • Like
Reactions: Flade

· Premium Member
1968 Ford Mustang Coupe | 302 | E-Style
Joined
·
401 Posts
Discussion Starter · #9 ·
First off, as always, yall are awesome!

I believe a lot of the vacuum lines under the dash are missing or incorrect in general so I do plan to run the new lines. There are two ports on the firewall (vacuum) and I understand one goes to the canister and the other goes to the water valve. I just need to connect them, wanted to run all the new lines so make sure there aren’t any leaks!

At this point, I need the hose to go from the heater core to the water pump, I have the small one to go from the other heater core port to the valve, then I need the hose from the valve to the manifold According to this diagram. @JW67Conv thanks for the info on those, will get the correct pre-bent ones from NPD. No rush to fix this, want to get all the right parts and have every component working.

I am just hoping all the servo’s under the dash work properly.
Here are a few pictures of the random parts I have -
 

Attachments

· Registered
Joined
·
8,201 Posts
Looking good. You are on the right path. Looks like someone added a couple check valves (non Ford). You really only need one on the line out of the vacuum canister to the manifold. It keeps vacuum in the system when there is low manifold vacuum. One thing to watch out for, I have found a number of documents the have the vacuum lines drawn or labeled wrong Including the Electrical Assembly manual.
 

· Premium Member
1968 Ford Mustang Coupe | 302 | E-Style
Joined
·
401 Posts
Discussion Starter · #11 ·
Okay, took some things apart today and learned a lot, the entire system itself is so much easier to understand once you dig into it! Removed all the old vacuum lines and trashed them. Installed the new ones according to spec, the chart made it super easy to follow the colors. Found the heater cable plastic part snapped off so I was happy I had another one - replaced it and all is good there.

A few things I have noticed, the actuator to open and close the defrost door is difficult to move by hand, I couldn't image any amount of vacuum being able to move it. Also the mounting tabs on the defroster vents are snapped so I had to zip tie them for now.

The bottom part of the A/C box is cracked, not sure if that matters or not. The big kicker, the passenger side is missing the flow tube entirely and the elbow to attach it to the vent so I need to order those as well - been waiting to order the heater hoses from NPD and I wanted to see what else I would need first.

Pictures attached - feel free to let me know if you see anything else I might need. In debate on what to do about the actuators, wonder if I need to replace the whole box - would really love to have a fully functional system here.
 

Attachments

· Registered
Joined
·
8,201 Posts
You need to pull the box and rebuild it with new seals. Good chance the defroster duct door is bent or rusted up. You can repair the box with fiber glass resin.
 

· Premium Member
1968 Ford Mustang Coupe | 302 | E-Style
Joined
·
401 Posts
Discussion Starter · #13 ·
You need to pull the box and rebuild it with new seals. Good chance the defroster duct door is bent or rusted up. You can repair the box with fiber glass resin.
Yeah I think that's a good idea. Going to pull it all out, clean and wire brush what I can, replace anything else! Will take longer but I want to do it right the first time. Also I am lucky that it's not connected, don't have to drain any coolant or anything -
 
1 - 13 of 13 Posts
Top